Abstract
Spray pyrolysis is a convenient method for fabricating BiVO4 photoanondes from a precursor solution. As the precursor solution of spray pyrolysis can significantly influence the nanostructure and the amount of oxygen vacancies of the final films, modifying the precursor solution is an efficient strategy for improving the photoelectrochemical (PEC) performance of BiVO4 photoanodes. Herein, an ultraviolet and ultrasonic treatment for modifying a vanadium precursor solution of spray pyrolysis was developed to produce efficient nanoporous BiVO4 photoanodes. By the simple treatment, the AM 1.5 photocurrent density of the photoanode reached 1.76 mA/cm2 at 1.23 V vs the reversible hydrogen electrode (RHE) for water oxidation, which is 12.3 times higher than the untreated BiVO4 photoanode. The good PEC performance was mainly attributed to the excellent charge separation that reached approximately 94.2% at 1.23 V vs RHE. Systematic studies revealed that the treatment for the precursor solution could tune the nanoporous structure and increase the amount of oxygen vacancies in the final films. This finding offers a facile and effective approach for fabricating efficient photoelectrodes for PEC water splitting.
Highlights
Photoelectrochemical (PEC) water splitting is a promising method to convert solar energy to chemical fuels.1–10 Monoclinic BiVO4 was shown as a fascinating photoanode material for water splitting, owing to the suitable bandgap energy (∼2.4 eV) and appropriate band edge positions.8–10 The theoretical solar-to-hydrogen (STH) efficiency of BiVO4 is about 9.2%.11,12 most reported STH efficiencies of BiVO4 photoanodes are far below the expected value because the material suffers from severe charge recombination.12–15 The total photocurrent densities (Jph) of the BiVO4 photoanodes are mainly determined by light absorption efficiency, charge separation efficiency, and charge transfer efficiency, that is, Jph = Jmax × ηabs × ηsep × ηtransfer.16 Charge separation efficiency is limited by the charge recombination in the bulk
As the precursor solution of spray pyrolysis can significantly influence the nanostructure and the amount of oxygen vacancies of the final films, modifying the precursor solution is an efficient strategy for improving the photoelectrochemical (PEC) performance of BiVO4 photoanodes
Since the light absorption is determined with the bandgap of the semiconductor and sluggish water oxidation kinetics can be eliminated significantly by loading proper oxygen evolution cocatalysts (OECs), enhancing the charge separation efficiency by suppressing the bulk carrier recombination is an important aspect for improving the PEC performance of BiVO4 photoanodes
Summary
Since the light absorption is determined with the bandgap of the semiconductor and sluggish water oxidation kinetics can be eliminated significantly by loading proper oxygen evolution cocatalysts (OECs), enhancing the charge separation efficiency (ηsep) by suppressing the bulk carrier recombination is an important aspect for improving the PEC performance of BiVO4 photoanodes.. Choi et al reported that nanoporous BiVO4 photoanodes produced by an electrochemical synthesis route manifested a high charge separation efficiency, which was over 90% at 1.23 V vs reversible hydrogen electrode (RHE).. Increasing the density of oxygen vacancies in nanoporous BiVO4 electrodes is an effective strategy to further enhance the charge separation efficiency.. The strategy of increasing oxygen vacancies in nanoporous BiVO4 photoanodes can significantly enhance the charge separation by reducing bulk carrier recombination. The nanoporous BiVO4 photoanodes with high charge separation efficiency can be achieved by the simple spray pyrolysis synthesis route
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